Heart failure is a condition effecting millions of people worldwide. Heart failure includes failure of either the left side of the heart, the right side of the heart, or both. Left heart failure can lead to elevated pulmonary venous pressure, which may cause respiratory problems, including shortness of breath and exercise intolerance. Left heart failure may be ascribed to a number of causes, including valve disease, systolic failure of the left ventricle, and diastolic failure of the left ventricle. The adverse clinical result of each of these conditions is similar; the heart failure leads to elevated pressure in the left atrium and elevated pressure in the pulmonary veins, impeding proper flow of oxygenated blood through the blood supply. Therefore, there exists a need to treat the adverse effects of elevated pulmonary venous pressure on the body.
Heart failure has been further classified as either systolic heart failure or diastolic heart failure. Diastolic heart failure refers to heart failure that is present without the presence of major valve disease even while the systolic function of the left ventricle is preserved. More generally, diastolic heart failure is failure of the ventricle to adequately relax and expand in order to fill with blood, causing a decrease in the stroke volume of the heart. Presently, there exist very few treatment options for patients suffering from diastolic heart failure. Therefore there exists a need for methods and devices for treating elevated pulmonary venous pressures caused by diastolic heart failure.
A few techniques have been disclosed for reducing elevated pulmonary venous pressure; however these techniques all suffer from critical deficiencies. For example, U.S. Published patent application Ser. No. 09/839,643 by Keren et al discloses the use of a complex an intra-atrial pressure relief shunt including a stented valve. This approach suffers from several deficiencies. First, the proposed treatment requires the implantation of a complex implant device, which increases the risk of various clinical complications and adverse events. The implant resides partially in both the left atrium and right atrium, and poses a risk of generating thrombus and releasing emboli into the left or right circulation.
Releasing emboli into the left circulation could lead to a myocardial infarction or stroke. Additionally, the valve apparatus requires moving parts, which increases the risks associated with long term implant material fatigue and device fracture. A device fracture could in turn lead to embolization of all or part of the implant. Additionally, the valve incorporated into the shunt has the potential to fail acutely, possibly leading to a rapid increase in the load on the left heart. The patient could conceivably experience a significant acute circulatory pressure overload caused by sudden closure of the therapeutic shunt, potentially leading to severe complications. Therefore, there still exists a need for a simple and effective means of treating elevated pulmonary venous pressures caused by heart failure.